How do I manually input transactions in a bank account that has been closed and I no longer have access to online statements?

Thank you for posting here in Community, @teamsage.

You can manually enter transactions on your bank directly on the register. 

Here's how: 

1. Go to the Accounting tab then Chats of Accounts.
2. Click View register, from there you have the option to create a transaction.

Image for reference.

To learn more about how to create transactions that can help you in the future, visit this link for video tutorials: Video tutorials for QuickBooks Online.

Let me know if you have additional questions. Feel free to post it here in Community, have a great day.

@teamsage 

"How do I manually input transactions in a bank account that has been closed and I no longer have access to online statements?"

If you can no longer import CSV or QBO or other formats file from the bank, you will need to manually enter it in the bank register. (Left Dashboard > Accounting > Chart of Accounts > Select the bank > Click View Register under Action column).

Refer to this very popular video tutorial for an instructional guide:

https://youtu.be/iLtOfEtpl48

I hope this helps!